Sana Sana / Reuters
According to Human Rights Watch, the attacks were part of the overall military strategy to retake the city.
Sophia Jones/The WorldPost
The probe shows the decision to use toxic weapons came from the very top.
The threat from chemical attacks may be limited, but the fear they create is real.
Ahmed Jadallah / Reuters
Up to 250 people may have died from exposure to chemical weapons, Amnesty International says.
No troops were injured in the shelling, officials told CNN.